This investigation is a study of the mechanisms by which bacteria evolve new enzyme abilities and acquire new metabolic pathways. Current concepts on the evolution of metabolic pathways are being tested experimentally using a lysogenic strain of Klebsiella aerogenes and certain of the unnatural and uncommon five carbon sugars as potential growth substrates. The project is attempting to demonstrate that mutations leading to hyperconstitutive production of ribitol dehydrogenase are gene duplications of the structural gene for ribitol dehydrogenase. In addition studies are continuing to develop an efficient and regulated pathway for the degradation of D-arabinose by this organism, while documenting the genetic changes required to create this pathway. The versatility of Klebsiella with respect to the five-carbon sugars as substrates, and present knowledge of the enzymatic pathways, enzyme activities, and regulation of the pathways, now combined with a system of genetic transfer, provides the opportunity to test experimentally current ideas on the means by which microorganisms adapt to new environmental conditions and acquire new metabolic abilities. BIBLIOGRAPHIC REFERENCE: Mortlock, R. P., Utilization of Uncommon Carbohydrates of Microorganisms, "Advances in Microbial Physiology, 13: 1-53. Ed. by A. H. Rose and D. W. Tempest. Academic Press, New York. Inderlied, C. C. and R. P. Mortlock, 1977. Growth of Klebsiella aerogenes on Xylitol: Implications of Bacterial Enzyme Evolution. J. Mol. Evol. (in press).